Triggering device for spark-gap and load focusing means



USING MEANS Dec. 27, 1966 s. BARBlNl TRIGGERING DEVICE FOR SPARK-GAP AND LOAD FOG Original Filed Oct. 27, 1964 4 Sheets-Sheet 1 Dec. 27, 1966 s. BARBINI 3,

TRIGGERING DEVICE FOR SPARK-GAP AND LOAD FOCUSING MEANS Original Filed Oct. 27, 1964 4 Sheets-Sheet 2 3 25 5 115 I/ I: y

FIGS 4 FIG.3

FlGb 6 2 3 /6 l, l/l FG. I 7 3f Dec. 27, 1966 s. BAR'BINI 3,2

TRIGGERING DEVICE FOR SPARK-GAP AND LOAD FOCUSING MEANS Original Filed Oct. 27, 1964 Sheets-Sheet 3 TD GT Tag cw- D i C 134 FIGB 5 United States Patent F 3,295,012 TRIGGERING DEVICE FOR SPARK-GAP AND LOAD FOCUSING MEANS Spartacus Barbini, Chaville, France, assignor to Compagnie Generale dElectricite, Paris, France Original application Oct. 27, 1964, Ser. No. 406,866. Divided and this application Oct. 22, 1965, Ser. No. 515,279

Claims priority, application France, Oct. 28, 1963, 952,065; June 4, 1964, 977,058 3 Claims. (Cl. 315-152) This application is a divisional application of my copending application Serial No. 406,866, filed October 27, 1964, entitled Triggering Device for Spark Gap.

The present invention has for its purpose to provide a solution to the problems arising from the necessity of quick closing of the electric circuits in which an electric energy storage must deliver a very large current into a relatively weak load under a very high voltage. The very quick passage of a very large electric energy is very difficult to achieve because the circuit breakers or the switches generally used to close the electric circuits do not possess the required characteristics, namely a steep enough rising front with a large enough closing capacity and a small enough control time constant.

In some cases, the sudden discharge of an electric energy storage into an impedance circuit relatively weak is obtained by means of electrodes between which occurs an electric are when the diiterence of potential between the electrodes exceeds the breakdown voltage.

Accordingly, the object of the present invention is a device, for the triggering of a spark-gap, more particularly remarkable in that the ionization of the dielectric between the electrodes of the spark-gap is caused by a device of the type designated by the abbreviation laser.

This method of application allows the utilization of electrodes with appropriate insulators, the position of the electrodes being, should the occasion arise, adjustable.

In a further embodiment of the present invention, the laser beam used for the triggering of the spark-gap may be set into action in such a manner that its energy comes in addition to the energy of the electric discharge in the spark-gap. It is thus possibleto realize devices of quick discharge in enclosures used for the studying of plasmas.

Further objects of the invention include embodiments of spark-gaps, combined with other devices. Other advantages and characteristics of the invention will appear from the following description, by no means limitative and which will be better understood with reference to the accompanying drawings on which:

FIGURE 1 represents the general diagram of a discharge circuit. 1

FIGURE 2 is a sectional view of-possible structures of electrodes.

FIGURES 3, 4, 5, 6, 7 show variants of the device according to the invention.

FIGURE 8 shows the application of the device according to the invention or the simultaneous triggering of several spark-gaps.

4 FIGURE 9 represents an example of application to a spark-gap divided into partial-gaps.

FIGURE 10 shows a variant of the device according to FIGURE 9.

FIG. 11 is a sectional view of a variant of application of the apparatus according to the invention.

On FIG. 1 has been represented, to facilitate the explanation, the diagram of a discharge circuit which is composed of an electric energy storage 1 (capacity) connected, on the one hand, to the earth, and on the other hand, to an electrode 2, the other electrode 3 being connected to the earth through the intermediary of a load.

Patented Dec. 27, 1966 "ice The load can be, for example, a gas tube 4 comprising two electrodes 5 and 6, the tube being full of a gas, the reaction of which is being studied to an electric discharge between the electrodes 5 and 6. The electric energy storage may be, for example, a capacitor loaded to kilovolts and storing an energy of the order of 100 kilojoules. The electric discharge in this tube is obtained when the electrodes are short-circui-ted by an electric arc, the producing of the electric are :being a function of the circumstances determined by the Pashens law.

The discharge in the tube 4 previously triggered then depends on the discharge between the electrodes 2 and 3 brought to a difierence of potential higher than the breakdown voltage.

This breakdown voltage can be considerably lowered by previous ionization of the gaseous dielectric between the electrodes. It depends, on the other hand, on the geometrical shape of the electrodes which can, 'by example, be made so as to make use of the effect called effect of points.

FIG. 2 represents schematically sections of different types of electrodes used in devices called spark-gaps.

The discharge of a circuit such as the one represented on FIG. 1 can be obtained by the lowering of the breakdown voltage caused by a partial ionization of the dielectric spa'ce comprised between the electrodes.

Different types of devices allow to ionize partially this dielectric space: the best known are those which make use of a radiation, such as X-rays, high frequency electromagnetic fields or sparking devices of the type of the sparking-plugs used in the internal combustion engines.

The spark-gap according to the invention can be embodied with numerous variants, the examples of which are given by the settings shown in the following figures.

The electrodes of the spark-gap can be symmetrical (23, FIGURE 3), the laser 15 being located outside. The shape of the electrodes depends on the position of the laser as also on the required circumstance of operation.

In the case of the FIGURE 3 the laser 15 used is advantageously a triggered laser, a focusing of the beam enabling not to direct this latter onto one of the electrodes but onto the volume of dielectric gas between the two electrodes. The electrodes can be housed in an enclosure 25 under a weak gas pressure easily ionizlable (cooperation of thermic tearing away of the metal electrons and of the gas ionization by heating), the enclosure being provided with a window allowing the passage of the luminous beam of the laser. The enclosure housing the electrodes can be under vacuum, in this case, then,

I the thermic tearing away of the electrons alone produces the triggering of the electric arc. Examples of these embodiments have been schematically represented on the FIGURES 4 and 5.

The locating of the laser outside the spark-gap offers many advantages by the fact that it does not set anymore the insulatingproblem of the laser control circuits. Moreover, in the case of triggered lasers, the luminous beam may be split into two parts, as in the FIGURES 6 and 7, one of them being directed to the spark-gap as it has been described above, the other part of the beam being used to produce the partial ionization of the gas which would be enclosed in the discharge tube constituting the load 3 of the electric circuit as shown on the FIGURE 1. According to the invention, other arrangements of the laser are possible; for example, the laser beam may cross the discharge tube 4, constituting the load of the circuit, before to hit the electrode 2 through an opening provided in the electrode 3 (FIG- URE 6).

It is possible to enlarge the application of such a 3, with several spark-gaps. In this case, the axis of a laser device crosses the spaces between the electrodes of several spark-gaps spaced out along said axis. In this case the laser beam is used as parallel beam or as a variant may be focused on the last spark-gap, in the space between the electrodes on one of the electrodes of this last spark-gap.

On another part, it is known that the price of a sparkgap for high voltage increases much more rapidly than its operating voltage. If it is possible to replace a sparkgap for U kilovolts by n partial spark-gaps in series, each operating under the'voltage U/n, the price of the installation will be considerably lowered for a convenient value of 11.

According to another characteristic of the invention a possible embodiment of such an arrangement would be to connect it partial spark-gaps in series and to place them along the axis of a laser beam which, at the moment of its appearing, will trigger all of them at the same time.

Preferentially the axis of the spark-gaps are set perpendicularly to the axis of the laser and are, or not, parallel to each other and the axis of the laser beam crosses each space between electrodes substantially in its middle. But one may deviate from these conditions without going out of the scope of the invention. The shapes of the electrodes and their spacing can be identical in all the spark-gaps or variable from one spark-gap to the other as well as the voltages. The spark-gaps may belong to different circuits.

In FIGURE 8, according to the axis of a laser 15 are alined n spark-gaps, among which four of them are repres'ented on the figure: the spark-gaps are constituted by the electrodes 121-131, 122-132, 123-133, 124-134. When the laser emits its radiation beam according to its axis, all the spark-gaps are simultaneously triggered in an extremely short time.

In the FIGURE 9, a source of direct voltage for example a loaded capacitor 1 under a voltage U can discharge itself into a load 4 through two spark-gaps 16, 17 and 18, 19 each of one being liable to absorb a voltage U/2. When a laser 15 emits its radiation the two spark-gaps are simultaneously triggered and the discharge occurs. The number of two spark-gaps has been chosen as a nonlimit ative example.

In the example of embodiment represented in FIG- URE 10, the four electrodes 116, 117, 118, 119 are alined, the three first ones being crossed by a channel where passes the beam emitted by the laser 15. The beam may be stopped by the surface of the fourth electrode 119. In this case the beam acts by ionization of the gases between the electrodes 116 and 117 on the one hand and 118 and 119 on the other hand, the action being in this second case increased by the impact of the beam onto the electrode 119. This embodiment which is not limited to two spark-gaps, allows a specially simple structure of the electrodes such as 117 and 118 which are for instance made of two spheres connected by a tube. A simplified construction of the electrode and of the in :sulators is thus obtained.

The invention is not limited to the examples of embodiments given above as illustrations; it applies generally to the triggering of at least two spark-gaps by means of only one laser beam.

In order to achieve a minimum impedance circuit, one is led to select coaxial arrangement apparatus comprising a gap of the plate spark-gap type.

FIGURE 11 is an example of an embodiment of the apparatus according to the invention.

The apparatus comprises a spark-gap, the plates 321 of which are located between the electrodes 310 and 311, the electrodes 310 being connected to the energy storage 1 while the electrode 311 is connected to the first electrode 312 of the discharge tube. The discharge tube comprises a housing 316 made Of an insulating material and which may either be fully transparent or be provided with observation windows. The other electrode 313 of the discharge tube is connected to the bottom of the cylindrical conductor 317 surrounding completely the whole of the apparatus. This conductor may be provided with one or several windows such as 314 and 315. These windows may be used for the observation of the phenomena occuring inside the discharge tube as well as for the ingress of beams of visible or invisible electromagnetic radiations. According to the invention, the apparatus comprises one or several lasers located inside or outside the coaxial assembly. The winding used for the magneti striction of the plasma within the discharge tubeis shown schematically in 309.

A counter-electrode 319, integral with the conductor 317 via an insulating member 318, is located laterally with reference to the spark-gap While a laser 320 is located outside said conductor so that the beam which it emits impinges on the counter-electrode after passing through the window 315 and the space between the plates 321.

The laser beam 320 is split into two beams 340 and 350, 'by the device 324 which may be a prism.

According to this embodiment of the present invention, the winding 309 provided to obtain the magnetic striction is controlled by a spark-gap of the type described as regards FIGURE 3, by means of one of the beams 340 or 350. As in the case of the FIGURE 8, the beam 340, for instance, crosses first the space comprised between the electrodes 351 and 352 of this spark-gap, and this allows to control absolutely simultaneously the striction winding and the discharge of the spark-gap between the electrodes 310 and 311. The setup represented in the FIGURE 11 gives then a perfect synchronization. Such an embodiment will be preferentially obtained with a very high energy triggered laser.

In the examples of embodiment of the invention described above the assumption was made that the luminous beam of the laser was impinging upon a surface, whether it was that of an electrode or that of a counter-electrode. This assumption must not be taken with a restrictive meaning: the embodiment of the device with a triggered laser is particularly advantageous in the cases of the above described examples since the nontriggered laser delivers only a relatively reduced luminous energy density. The use of triggered lasers allow a focusing of the luminous beam and hence the setting in action of higher energies: the heating of the gas is then obtained without any previous heating of a metallic surface, whether constituted by an electrode or by a -counter-electrode. The application of the triggered lasers is particularly advantageous in the case of the device embodied according to FIG. 11 and it is in no way beyond the scope of the present invention. Furthermore, it is remarkable that the distant and external triggering of the main setups described in this patent, allows a very great security of use and operation this being particularly valuable when very high voltages and very high energies are involved.

What I claim is:

1. A device for controlling quick discharge of an electric energy storage means in an electric circuit comprising a relatively weak load under high voltage comprising two electrode means defining a spark gap, a discharge tube having two electrodes and forming a load for said circuit, a cylindrical housing means having a metal portion and partially enclosing said electrode means and said discharge tube, a first conductor connecting one of said electrode means with one of the electrodes of said discharge tube, a second conductor connecting the second electrode of the discharge tube with said metal portion of said housing means and a third conductor connecting the second electrode means to said electric energy storage means, a metal lic body located adjacent said spark gap, a laser having a high density energy luminous beam directed onto the surface of said metallic body for selectively causing a discharge across said gap, and means associated with said 5 6 discharge tube for focusing the electric discharge Within ly connected with said winding, said laser beam being disaid tube. rected across said second spark gap.

2. A device according to claim 1, wherein said focusing means comprises a Winding concentric with said discharge No references tube and immediately outside thereof. 5

3. A device according to claim 2, wherein the excitation JOHN HUCKERT Primary Examinerof the winding is controlled by the discharge of a second I, D, CRAIG, Assistant Examiner. spark gap between a second pair of electrode means serial- 

1. A DEVICE FOR CONTROLLING QUICK DISCHARGE OF AN ELECTRIC ENERGY STORAGE MEANS IN AN ELECTRIC CIRCUIT COMPRISING A RELATIVELY WEAK LOAD UNDER HIGH VOLTAGE COMPRISING TWO ELECTRODE MEANS DEFINING A SPARK GAP, A DISCHARGE TUBE HAVING TWO ELECTRODES AND FORMING A LOAD FOR SAID CIRCUIT, A CYLINDRICAL HOUSING MEANS HAVING A METAL PORTION AND PARTIALLY ENCLOSING SAID ELECTRODE MEANS AND SAID DISCHARGE MEANS WITH ONE OF THE ELECTRODES OF SAID DISCHARGE TUBE, A SECOND CONDUCTOR CONNECTING THE SECOND ELECTRODE OF THE DISCHARGE TUBE WITH SAID METAL PORTION OF SAID HOUSING MEANS AND A THIRD CONDUCTOR CONNECTING THE SECOND ELECTRODE MEANS TO SAID ELECTRIC ENERGY STORAGE MEANS, A METALLIC BODY LOCATED ADJACENT SAID SPARK GAP, A LASER HAVING A HIGH DENSITY ENERGY LUMINOUS BEAM DIRECTED ONTO THE SUR- 